Global Climate Change (Climate Disruption/Ozone Depletion)

1. Global Climate Change(Climate Disruption/Ozone Depletion) CHAPTER 19

2. A History of Earth’s Climate

3. Greenhouse Effect • When a hemisphere is facing the sun, about half of incoming solar radiation passes through the atmosphere and warms the Earth. • At night, that heat is radiated from the Earth’s surface back towards the atmosphere.

4. The atmosphere creates a greenhouse effect, absorbing and re-radiating some of that heat back towards the Earth. • Greenhouse gases contribute to this effect, and include: • Carbon dioxide • Methane • Nitrous oxide • CFCs • The greenhouse effect keeps the Earth’s temperatures within a habitable range.

5. Mars has a much thinner atmosphere, with no greenhouse effect. • A Martian summer daytime high near the equator may approach 70°F. • At night, the same location would experience a low of -100°F.

6. The Precambrian Period • The Earth’s atmosphere has undergone many changes throughout its history. • During the Precambrian Period, from 4.6 billion to 540 million years ago, the Earth’s atmosphere was mostly carbon dioxide and nitrogen. • The earth was populated by many species of single-celled prokaryotes; the Archaebacteria Cyanobacteria bloom, Lake Erie.Photo by Thomas Archer

7. A new life form called cyanobacteria (Domain Eubacteria) evolved the ability to perform photosynthesis, absorbing carbon dioxide and releasing oxygen. • Photosynthesis weakened the greenhouse effect due to the removal of carbon dioxide and oxidation of methane. • This triggered the first and longest ice age ever faced by the Earth. • The “snowball Earth hypothesis” suggests the planet was mostly covered in ice.

8. Ice Ages • An ice age is a period of time where the Earth’s overall surface temperature is lowered enough that glaciers form at the poles and in mountainous areas. • The Earth has experienced at least 5 major ice ages. Average global temperatures over the past 2.4 billion years.

9. Within each ice age, glaciers will expand and shrink. • During glacial periods, glaciers are growing and advancing. • During interglacial periods, the overall climate is warmer, leading the glaciers to retreat. • We are currently in an interglacial period of an ice age. Average Greenland/Antarctic temperatures over the past 450,000 years.

10. Proxies • Temperature data prior to the 19th century is the result of proxies, or indirect measurements. • The main proxy is ice cores drilled into the glaciers in Antarctica and Greenland. • Dissolved bubbles of atmosphere in each layer are analyzed for the presence of atmospheric gases

11. Two sets of data can be extracted from studying ice core data: • The temperature can be estimated by studying the relative amounts of oxygen isotopes present in the water in the ice. • The concentrations of carbon dioxide, methane, and nitrogen oxides are measured directly by sampling the air bubbles. Photo by Pete Bucktrout, courtesy British Antarctic Survey.

14. The last glacial period on Earth ended about 10-20 thousand years ago. • The overall temperature has been stable since, a few exceptions triggered by natural phenomena.

15. Medieval Warming and Little Ice Age • The Medieval Warm Period lasted between about 950-1250 C.E., with warmth in some regions exceeding the current post-industrial era. • Historical events partially tied to this period include: • Vikings being able to cross ice-free seas and colonize southern Greenland and Newfoundland. • High crop yields and economic prosperity throughout much of Europe and Asia. A reconstructed Viking settlement, L’Anse aux Meadows, Newfoundland.

16. The Little Ice Age was a period of cooling that lasted from the 16th-19th centuries. • The Viking colonies in Greenland failed and were abandoned. • North American Indian tribes formed alliances in response to food shortages. • The River Thames frequently froze over in the winter, leading to frost fairs. • A straight called the Great Belt froze over, allowing Sweden to march across it and invade Denmark (The March Across the Belts) The Frozen Thames, 1677.

17. Natural Causes of Climate Change • The Earth periodically undergoes a series of 3 changes called Milankovitch Cycles that affect the amount of global solar radiation received: • Shape of its orbit around the sun (~100,000 years) • Tilt of the Earth’s axis (~41,000 years) • Wobbling of the Earth’s axis (~23,000 years)

18. Volcanic eruptions release sulfur dioxide and particulates that scatter solar radiation, causing a cooling effect. • In 1816, Mount Tambora in Indonesia erupted, causing snow to fall in June in North America, resulting in crop losses and food shortages.

19. Sunspots are darker areas on the sun’s surface created by intense magnetic fields. • The sun emits slightly more radiation when more sunspots are present. • The sun emits slightly less radiation when fewer sunspots are present. • The number of sunspots fluctuates from a maximum to minimum number every 11 years.

20. The Great Ocean Conveyor Belt is an underwater current fueled by the mixing of warm and cold salt water. • An influx of cold freshwater from melting land ice could disrupt this flow. • The release of heat by this system keeps Western Europe warmer than other areas at the same latitude.

21. The El Niño-Southern Oscillation cycle is a periodic warming and cooling of surface ocean temperatures in the Pacific Ocean. • This warm water affects evaporation rates, influencing temperatures and precipitation levels throughout the world.

22. Evidence of Climate Change • Since 1958, daily measurements of atmospheric carbon dioxide levels have been taken at an observatory on Hawaii. • Hawaii was chosen to avoid the influences of large forests or cities.

23. Carbon dioxide levels fluctuate within each year, depending on the season of the Northern Hemisphere. • Slightly higher CO2 in the winter. • Slightly lower CO2 in the summer.

24. In 1988, the United Nations set up the Intergovernmental Panel on Climate Change (IPCC) to assess climate change: • Gathering evidence that it is taking place • Assessing impacts and future risks • Providing options for adapting and mitigating to its effects. • According to the IPCC 2014 report: “Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice and rising global average sea level.”

25. Both land and ocean surface temperatures have increased since the industrial revolution. • There has been a 0.9°C increase in average surface temperatures. • 17 out of 18 of the warmest years since 1880 have occurred since 2001. • The area of greatest warming has been in the Arctic.

26. Sea ice is frozen seawater that floats on the ocean’s surface. • The minimum sea ice extent in the Arctic is measured every September. • This has decreased steadily, with an ice-free Arctic expected by 2030-2040.

27. Ice sheets are any permanent layers of ice covering a tract of land, especially in the polar regions. • Antarctic ice sheets are losing 127 Gigatonnes(Gt) of ice per year. • Greenland ice sheets are losing 286Gt/year.

28. Sea level worldwide is increasing, primarily due to two factors: • Water flowing in from melting ice sheets. • Thermal expansion: the tendency of water to expand in volume as it warms.

29. Impacts of Climate Change • The increase in surface temperature has influenced many aspects of plant growing seasons.

30. Warmer temperatures have increased the range of many pest insects. • Mosquitoes that spread diseases like malaria and West Nile Virus have expanded ranges. • Pine bark beetles have begun infesting boreal forests east of the Rocky Mountains.

31. Coral bleaching occurs when coral polyps eject the symbiotic algae that live with them under stressful environmental conditions. • Ocean water is becoming more acidic as it absorbs carbon dioxide. • Ocean water overall is becoming warmer.

32. Hurricane frequency and intensity has increased since 1980. • The exact link between hurricanes and climate change is uncertain.

33. Great Ocean Conveyor • Scientists fear the Great Ocean Conveyor may weaken or be stopped as cold water flows in from Greenland. • This would cause rapid cooling throughout Western Europe.

34. Melting of ice sheets into ocean water has lowered the overall albedo of the Arctic. • Albedo is a measurement of how reflective a surface is. • A lower albedo in the Arctic causes warming to take place even faster, creating a positive feedback loop.

35. Mountain glaciers, like land ice, are shrinking worldwide. A 1870 postcard of the Rhone glacier in Switzerland contrasted with a 2006 view. Source: New York Times

36. The Himalayan glaciers are expected to decline by 70% or more by 2100, endangering irrigation, drinking water, and hydropower throughout Southeast Asia.

37. The hydrologic cycle describes the movement of water through evaporation, precipitation, runoff, and infiltration. • The phase changes of water in this cycle are driven by heat. • More heat in the atmosphere leads to… • A higher rate of evaporation (from land and sea both). • A greater capacity of the atmosphere for holding moisture.

38. Climate change has the paradoxical effect of increasing the rate of both drought and heavy precipitation events.

39. The increase in atmospheric moisture can also fuel blizzards during the winter months.

40. As the ocean level rises, coastal cities become more at risk of: • Increased erosion of beaches and shorelines. • Flooding from intrusion of ocean water. • Increased risk of damage from storm surges. Sea wall, Malé , Maldives.

41. Projected Effects of Global Warming and Resulting Changes in Global Climate Stepped Art Fig. 19-7, p. 507

42. Did We Cause It? • Determining our impact on climate change revolves around the idea of anthropogenic greenhouse gases – ones that were released by human activity. • This can be established by comparing the three isotopes of carbon present in molecules of carbon dioxide. • The majority of plants only use carbon-12 in photosynthesis. • Some plants like sugar cane, corn and pineapple use carbon-13 as do succulent plants. • Fossil fuels are plant or algae derived, from areas where large amounts of those organisms have grown over centuries so burning them releases carbon dioxide that only contains carbon-12. • The ratio of carbon-12 to carbon-13 has increased since the industrial revolution.

43. There is near-unanimous consensus (97%) amongst scientists that climate change is occurring and that humans are at least partially responsible for it. • Most scientific organizations have also endorsed this position: • See the list on your extra handout Temperature data from four international science institutions.

44. Solutions • Responding to climate change involves two different approaches: • Migitation strategies are designed to reduce emissions and stabilize the levels of greenhouse gases already in the atmosphere. • Adaptation involves adjusting our lives and society to the expected future climate.

45. Mitigation • The ocean, forests, and soil can be used as carbonsinks, meaning they absorb and retain carbon dioxide from the atmosphere. • Reforestation of areas that have been clear cut. • Fertilizing areas of the ocean to promote algae growth. • Protecting and restoring wetlands. Experimental reforestation of the Ashio copper mine, Japan. Photo by Robert Stolz, japanfocus.org

46. Reducing greenhouse gas emission requires major societal changes: • Switching from fossil fuels to renewable energy sources. • Consuming less beef, as cows release large amounts of methane. • Finding alternatives to ammonium fertilizer, which can be converted into nitrogen oxides. A gas-catching backpack used by researchers measured 800-1000L of emissions from an average cow per day. Cows are responsible for 35-40% of methane emissions.

47. Geoengineering • Geoengineeringis the study of intentionally and artificially changing natural processes of the Earth. • Solar radiation management uses reflective surface materials to reflect more back into space. • Stratospheric aerosols are reflective molecules that would be injected into the stratosphere. • Carbon capture and storage is the process of capturing carbon dioxide produced from large point sources, such as coal-burning power plants and depositing it underground. SchwarzePumpe power station and carbon capture facility, Spremburg, Germany.

48. Legislation • In 2009, the U.S. House of Representatives voted in favor of a carbon dioxide cap-and-trade bill. • A cap would be set on the maximum amount of carbon pollution that can be produced by a single facility. • Companies could trade carbon credits in exchange for money, creating an economic incentive. • This bill was defeated in the Senate, due to concerns about increased energy costs and its effect on the economy.

49. Under the Obama administration, the EPA, began publishing restrictions on carbon pollution that can be released from power plants. • The agency is using authority granted by the Clean Air Act to treat carbon dioxide as a pollutant. • These restrictions were rolled back under the Trump administration. • Permanent regulations must originate from Congress.

50. Many local governments, especially in South Florida, are already actively spending money on climate change adaptation, including: • Sea wall construction • Erosion barriers to protect beaches • Raised roadways • Stormwater pumps